Amplifying system, method, and apparatus



April 5, 1932. F. MEYER ET AL 1,852,182

AMPLIFYING SYSTEM, METHOD, AND APPARATUS Filed Feb. 5, 1928 Patented Apr. 5, 1932 UNITED STATES PATENT' OFFICE FRIEDRICH :MEYER AND HANS JOACHIM: SPANNER, F BERLIN, GERMANY, ASSIGNORS, BY MESNE ASSIGNMENTS, TO EDWARD H. LOFTIN, 0F NEW YORK, N.. Y.

AMIIEILIIEYINGA SYSTEM, METHOD, AND APPARATUS Application filed February 3, 1928, Serial No. 251,522, and in Germany August. 18,1926.

An application has been filed in Germany, August 18, 1926.

This invention relates generally to amplifying systems, and more particularly to a system for the selective multiple amplifica-v tion `of high frequencycarrier currents modulated at lower or audible frequency.

An object of the invention is multiple selective high frequency amplification in a system lo employing a flesser number of selective circuits than steps of amplification, and particu- 1 larly a single selective or tuning circuit yfor a multiplicity of steps of high frequencyr step of amplification in that portion of an amplifying system intended for high frequency amplification of a complete system further' including detection andV low frequency amplification, and to perform the detection as a separate step and, in general, the low frequency amplification in independent separate steps. The present invention reduces these prior complications in many respects as will be more fully pointed out in connection with the one figure of the drawing.

The figure diagrammatically illustrates the invention employed as a radio receiver; for example, a broadcast receiver intended to cover a rather wide range of wave-lengths. 4It includes an antenna A connected to ground Gr through a variable condenser C1 and a primary coil L1,a'll of general arrangement common in practice. Three electrode amplifyg' ing tube VTi has aninput circuit L2@2 the only tunable circuit of the system, this circuit being coupled to the antenna through coupling with antenna coil L1, and being l tunable through the desiredrange of high frequencies or wavelengths. A high resist- :ance R1 couples VTl'with a second amplifying tube VT2 through al condenser G3 shunted by a grid leak resistance Rl usual in such 50 systems.

Heretofore 1t has been the general practice Y to employ a separate tuning circuitffor each By reason of the capacitive reactionV of the output circuit of VT1, created `by the'lresistance R1 and 'its distributed capacity as well as capacitive effects of other connections'of the output circuit, a high frequency reaction through the internal capacity of the tube unfavorable to amplication is had, so that without modification the amplifying of rhigh frequency in this tube is poor. The difficulty is overcome however by including in the output circuit coil L3 coupled to input coil L2, whereby enough energy 'maybe selectively fed back to the input circuit to overcome more or less the unfavorable feed back through the tube, thereby causing selective circuit LZCZ to not only act as a selective input to ltube VTl, but further act to cause the tube to selectively highly amplify. There therefore results a selective high difference of potential across resistance R1 for transfer to tube VT2. I f 70 Tube .VT2 also includes ahigh resistance R2 in its output, and therefore like VTl is inherently a poor high frequency amplifier, and wholly a non-selective amplifier. The `difficulty is again overcome by inserting a coil L44 in the output circuit coupled to the tunable circuit L2C2, either independently of or vin associat-ion with coil L3. This coupling succeeds in modifying the unfavorable feed back through the internal capacity of tube VT2, thereby making it a second effective, selective amplifier of high frequency currents for transfer across` resistance R2 through condenser CS to tube VTS. A

Tube VT3 includes a high resistance R3 in its output, and acts like the precedingJ tubes. A variation in the feed back connection is shown in that a connection is made to the antenna through the variable condenser C5, and may include a variable inductanceL5 forgpo a degree of phase changing. In this ar-` rangement the coupling to tunable Vcircuit L202 is had through antenna coil L1.

It is of course understood that` all couplings must be given .proper polarity to se- Vcure the results described `asl well as'propery degrees of coupling. A final adjustment .to prevent oscillation production may be 4had in variable condensers C1 and C5, or variable inductance L5, particularly if y found that 10U varyingcfrom one wave length range to another brings about oscillation in tuning in one sense, or results in too much loss of amplification in tuning in the opposite sense.

It is well known that vacuum tubes rectify no matter how carefully adjusted towards pureamplifi'cation, so that each tube ,of the system engages in some rectification. There therefore passes through the system from tube `-V T1 a rectifying action effectively transferred forwardby the high resistances R1, R2 and R3, ust as if the system were a so-called resistance coupled amplifier. 'As a result there reaches loud speaker or other translating device 'LS a current so amplified and modified that the low frequency modulations yare effective thereon, and it makes no material `difference whether this effect is' viewed asa continued high frequency amplification posite action.

with increasingly effective rectification, or

separated high frequency amplification and low frequency amplification as rectification takes place, or a composition of the two effects, or any other.characterization of com- Ve-have'found that such a system gives an overall result in selectivity and amplification (no -matter what kind) equivalent tomuch more-*elaborate systems involving several stagesof so-calledy tuned radio frequency amplification,detection and several -stagesIof laudio amplification. VItis obvious'thatmany difiiculties areobviated Vvand much material saved.

.potential Vfor this tube would probably be` employed. It has also been found that some advantages are had through increasing the capacities of the linking condensers C3, CS and C3 asr the-output end of the system is 1 approached.

While we have described our invention in Aconnectionwitha radio receiving system we fao do not intend any limitations by reason of the choice merely for illustrative purposes. Its

Vscope is defined-inthe appendedk claims.

Havingdescribedl our invention, we claim: '1. A system for the'mult1ple selective ainplification of alternating currents including a plurality of'amp-lifiers linked in cascade through non-selective couplings, a tunable in- Y,'put'lci'rcuit at the origin of thesystem, andseparatemeans regeneratively coupling each of the several output circuits of said amplifiers to said tunable .circuit,whereby said circuit selectively .controls the-amplification of 'all of said amplifiers. l

' 2. A system for the multiple selectiveamplification of alternatingcurrents including a. 'plurality-ofampliers linked in "cascade fthrough thigh fresist'ances, a tunable inp-ut circuit for said system, and separate means regeneratively coupling each o-f the several output circuits of said amplifiers yto said tunable circuit, whereby said circuit singly selectively controls the amplification ofl all'of said amplifiers. f

8. A system fo-r the composite selective multiple amplificationand detection of high frequency carrier currents modulated at lower frequency including a seriesof three electrode vacuum tubes connectedk in cascade through non-selective couplings capable of transferringrectified current effects, a tunable input circuit for said series of tubes, means regeneratively coupling each of a plurality of the output circuits'of said tubes to said tunable circuit, and a translating-device for said lower frequency modulations at the output of said series. Y f l Y 4. The composite method offselectively amplifying and detecting high frequency alternating currents modulated at lower frequency which .includes simultaneous, progressive, selective regenerative `.amplification yand rectification of said currents, lnon-selectively transferring .saidamplified currents in rectified form from stage to stage of said process, and finally translating said currents so modified into yresponses .characteristic of said lower frequency modulations.' l f 5. In a selective amplifyingl system the combination-of afpair of three electrode vacuum tubes aperiodically coupledin cascade, a tunable/circuit connected to the input elecytrodes of the leading'tube of said cascade,

. an` aperiodic output system for the .following tube offsaid cascade, and separate means associated withitheplatecircuit ofv-each tube regeneratively coupling the output systemsof each of said tubes to said tunable circuit.

6. In a selective amplifying system the combination of a pair of three relectrode'vacuum tubes connected in cascade, a tunable input circuit for the leading tube of said-cascade, an output system for the following tube of said cascade, the output systems of both of' said tubes being capacitive in reaction-tov currents of frequency range covered by saidtunableinputfcircuit, and separate means regeneratively coupling the ouput systems of rboth of said tubes to said tunable circuit.

.7. In a selective amplifyingV system the combination of a plurality of three electrode vacuum tubes connected in cascade through aperiodic coupling systems, a tunableinput circuit for the leading tube of saidfcascade, means electromagnetically coupling each of the output systems ofsaid tubes to'said tunable circuit. v

8. In a selective cascade amplifying system th-e combination of a plurality of threeelectrode vacuum tubes, a tunable -input circuit :for the leading tube of :the cascade, vmeans linking said tubes in cascadecapacitively reactive to currents of frequency range'c'overe'd lli) by said tunable circuit, and electromagnetic means regeneratively coupling the output system of the first tube and one or more succeeding tubes of the cascade to said tunable circuit. p

9. In a cascade system for progressively amplifying and detecting high frequency currents modulated at lower frequency the combination of a plurality of three electrode vacuum tubes, a tunable input circuit for the leading tube of the cascade, aperiodic interstage couplings between said tubes including capacity elements conductively isolating the output electrode of a preceding tube from the input electrode of a coupled succeeding tube, the capacity values of said elements progressively increasing from stage-to-stage from input towards output, and means regeneratively coupling the output systems of one or more of said tubes tosaid tunable circuit.

10. In a cascade system for progressively amplifying and detecting high frequency currents modulated at audible frequency the combination of a plurality of three electrode vacuum tubes, a tunable input circuit for the leading tube of the cascade, high resistance interstage couplings between said tubes, the interstage coupling connections including capacity elements conductively isolating the output electrodey of a preceding tube from the input electrode of a coupled succeeding tube, the capacity Values of said elements progressively increasing from stage-to-stage from input towards output, means regeneratively coupling the output system of the leading tube and of one or more of the succeeding tubes to said tunable circuit, and a translating device in the output of said system.

11. In a cascade selective amplifying system the combination of a plurality of three electrode vacuum tubes, a tunable input circuit for the leading tube of the cascade, an antenna system coupled to said circuit, aperiodic interstage couplings between said tubes, and means regeneratively coupling two or more of the output systems of said tubes to said tunable circuit, Said means including connections for coupling the output system of at least one of said tubes to said tunable circuit by way of the coupling between the antenna system and said circuit.

FRIEDRICH MEYER. HANS JOACHIM SPANNER. 

